Up to now, as the physical quantity sensor of this type, an acceleration sensor for detecting acceleration has been proposed (for example, refer to Patent Literature 1).
The acceleration sensor is configured with the use of silicon on insulator (SOI) substrate on which the buried insulating film and the semiconductor layer are laminated on the support substrate in order. In the semiconductor layer, a comb-shaped movable electrode and a comb-shaped fixed electrode that faces the movable electrode are formed, and a portion of the semiconductor layer partitioned from the movable electrode and the fixed electrode forms a peripheral part. A through-hole that penetrates through the peripheral part and the buried insulating film and reaches the support substrate is formed in the SOI substrate in a thickness direction (a stacking direction of the support substrate, the buried insulating film, and the semiconductor layer) of the SOI substrate, and a through-electrode that is electrically connected to the support substrate is buried in the through-hole.
The cap is formed of a semiconductor substrate or the like, and is formed with a contact part so as to receive a predetermined potential from an external circuit. The cap (semiconductor substrate) is joined to the semiconductor layer through a conductive film or the like so as to be electrically connected to the through-electrode formed on the SOI substrate. In other words, the cap (semiconductor substrate) is joined to the semiconductor layer through the conductive film or the like so as to be electrically connected to the support substrate through the through-electrode formed on the SOI substrate.
In the acceleration sensor of this type, the cap is maintained at the predetermined potential through the contact part, and the support substrate is maintained at the predetermined potential (the same potential as that of the cap) through the through-electrode. For that reason, the potentials of the cap and the support substrate can be restrained from being varied due to disturbance noise and the like, and an output variation can be restrained from occurring.
The acceleration sensor is manufactured as follows. Firstly, the SOI substrate in which the support substrate, the buried insulating film, and the semiconductor layer are laminated on each other in order is prepared. Next, the through-hole that penetrates through the peripheral part and the buried insulating film, and reaches the support substrate is formed in the SOI substrate, and then a metal film is buried in the through-hole to form the through-electrode. Then, reactive ion etching is performed to form the movable electrode and the fixed electrode in the semiconductor layer. The contact part is formed on the cap (semiconductor substrate). Thereafter, the semiconductor layer and the cap are joined to each other so that the support substrate and the cap (semiconductor substrate) are electrically connected to each other through the through-electrode formed on the SOI substrate, as a result of which the acceleration sensor is manufactured.